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Thursday, September 20, 2012

Antarctic sea ice a big deal? tamino shoots it down in "Poles Apart"

Poles Apart

As most of you are aware, Arctic sea ice has shrunk dramatically over the last several decades, because of man-made global warming. This year it has broken the records for lowest area, lowest extent, and lowest volume. Perhaps more to the point, those records were broken not by a little — not even by a modest amount — the were broken by a helluva lot. Yes, a hell of a lot. The loss of Arctic sea ice has been nothing short of astounding.

How have the fake skeptics of global warming responded? By changing the subject, of course.
Perhaps the most ridiculous example (by which I mean, worthy of ridicule) is onhcubed’s blunderblog. And what does he change the subject to? This:

Antarctic sea ice set another record this past week, with the most amount of ice ever recorded on day 256 of the calendar year (September 12 of this leap year).
Wow! Stop the presses! Extra!!! Extra!!! Read all about it!!! Antarctic sea ice reaches record high for this day of the year!
What a shame for that poor, poor, unimpressive Arctic sea ice. All it managed to do this year was set the record for lowest sea ice extent for a single day of the year for every day since July 28th. Yes, that’s the last few days of July, the entire month of August, and the entire month of September — so far. All it did was break the all-time record. All it was able to do this year was go below the pre-2012 all-time record 26 times — so far.
Yeah. The previous paragraph is sarcasm.
If that sarcastic exposition gives you the impression that it’s the “record” in Antarctica that’s unimpressive — then you got the right impression. But that won’t stop fake skeptics from exaggerating its importance, trumpeting it as though it were a major event. They really don’t have much choice … that’s all they’ve got.
They want to compare Antarctic sea ice to Arctic sea ice? Okay.
Here’s that “daily record high” in Antarctic sea ice (using daily extent data from NSIDC):
The data from 2012 is shown in red. If you’re color-blind, you’ll have a damn hard time telling which line is for 2012.
It might look like 2012 just barely broke the all-time record, but actually it didnot. It just barely missed. Here’s a close-up view of the recent maximum:
This year’s peak is certainly above average. But it’s nowhere near “astounding.” In fact, if it weren’t in red color, or if you’re color-blind, you could have trouble picking out which line is 2012 even in this expanded view.
Here’s the all-time record low in Arctic sea ice:
Even if you’re color-blind, you’ll still have absolutely no trouble picking out the 2012 line. It’s the one at the bottom. To be unable to see it, you’d have to beactually blind.
I’m fond of emphasizing trends rather than individual events (climate over weather and all that). For that purpose, one strategy is to study sea ice anomaly. Doing so removes the annual, seasonal cycle from the data. Here’s the sea ice extent anomaly data, for the Antarctic (in blue) and the Arctic (in red), which reveals that both have shown an overall trend, in opposite directions:
Which trend is more impressive? Let’s take a closer look:
How about the annual peaks, both high and low? Here are the annual wintertime maxima for both the northern and southern hemispheres:
The Antarctic maxima have increased. But the Arctic minima have decreased — faster.
But the real story is the annual summertime minima. Here they are for both hemispheres:
The Antarctic minima have increased, but only very slightly. But the Arctic minimum this year was only half what it used to be.
Really, there’s no comparison. But fake skeptics insist on making a comparison, because when they leave out the details it gives them something to talk about. And that’s all they’ve got.
Here’s the volume of Arctic sea ice at its summer minimum:
Arctic sea ice minimum volume has decreased by over 75%. Let me repeat that: by over 75%. That’s front-page news. The Antarctic setting a record-high-for-this-day-of-the-year is not.
Let me close by paraphrasing hcubed’s blunderblog:
Why is everybody talking about Michael Phelps’ olympic swimming medals? Florent Manaudou of France won the 50-meter freestyle gold medal in 2012 — why don’t I read about that on the front page of the New York Times? 

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